Jerod Mayo has played in 12 games for the Patriots since 2013. (NFL Game Rewind)

The New England Patriots brought in linebacker Rolando McClain for a free-agent visit this week. And while the 25-year-old has since returned to the Dallas Cowboys on a one-year deal reportedly worth up to $4 million, New England’s off-the-ball interest could be telling at this stage in the game.

According to Jeff Howe of the Boston Herald, the Patriots offered McClain a one-year, $4 million contract. But the 12-game starter in 2014 left without signing, and ultimately agreed with the Cowboys on a comparably structured deal Wednesday.

McClain now is back in a situation he enjoyed a comeback year in, after spending the 2013 season out of football. That familiarity could have very well factored into his decision, as he should remain in the mix as Dallas’ middle linebacker, allowing the injured starter he replaced, Sean Lee, to slide over to the weak side.

In New England, McClain’s spot on the depth chart would have been far less certain in the long-term. Yet, on the other side, the Patriots’ off-line linebacker spots are also uncertain at this time.

A team captain, two-time Pro Bowler and green dot of the defense, Jerod Mayo has been limited to 12 games due to pectoral and patellar tears dating back to 2013. The 29-year-old’s future performance is hard to project in result, as he’s been placed on injured reserve before November in each of the last two seasons.

In addition, the fellow former first-round pick who supplanted Mayo as the defense’s eyes and ears in 2014, Dont’a Hightower, underwent labrum surgery this offseason. He is expected miss the next six to seven months after turning in his best season as a pro, sugaring the A-gaps, finding the run fits and dropping into coverage in the flats and the hashes.

Both players are variables the Patriots will have to be patient with.

Their recoveries, in turn, figure to leave coach Bill Belichick and New England’s personnel department looking for serviceable depth.

That search likely factored not only into the Patriots’ interest in McClain, but also former Tennessee Titans linebacker Colin McCarthy, who visited New England shortly after free agency opened in March.

McCarthy remains a free agent. And as it stands now, New England’s pool of linebackers under contract remains 10 deep.

Jerod Mayo, 29 – First-round pick in 2008

Dont’a Hightower, 25 – First-round pick in 2012

Jamie Collins, 25 – Second-round pick in 2013

Darius Fleming, 25 – Former 49er, signed as free agent in 2014

Chris White, 26 – Former Lion, Bill, claimed off waivers in 2013

Deontae Skinner, 24 – Undrafted signing in 2014

Cameron Gordon, 23 – Undrafted signing in 2014

James Morris, 23 – Undrafted signing in 2014

Eric Martin, 23 – Former Brown, signed to practice squad in 2014

Jonathan Freeny, 25 – Former Dolphin, signed as free agent in 2015

Mayo and Hightower can be penciled in for September and perhaps part of training camp. And 2013 second-round pick Jamie Collins certainly will be, after rising fast during his second NFL season, finishing with 116 tackles, four sacks, four forced fumbles and two interceptions while logging the fourth-most snaps on the defense.

But behind that trio, there are seven.

Jonathan Casillas, who was acquired in the midst of the 2014 season and went on to carve a niche on special teams and as a third linebacker, is not one of them. He signed with the New York Giants this offseason, and it is unclear just whom will step into his place next season.

The Patriots have Darius Fleming, Chris White and Deontae Skinner coming back after all three made reserve contributions on the 53-man roster during New England’s Super Bowl run.

Fleming, who overcame two torn ACLs during his tenure with the San Francisco 49ers, was elevated from the Patriots’ practice squad in 2014 and helped out on special teams while also recording 38 snaps on defense, per Pro Football Focus. White, a core special-teamer for New England the last two years, has only garnered a handful of defensive snaps with the team over that span. And Skinner, an undrafted free agent who started at inside linebacker for several weeks due to injuries and registered a sack, ended the year on the practice squad.

Joining them on the back end of the depth chart is Cameron Gordon and James Morris, after both undrafted rookies resided on injured reserve for all of 2014.

Former Cleveland Brown Eric Martin is also in the fold, after the Nebraska product was a late addition to the practice squad this past winter. And rounding out the list next to him is Jonathan Freeny.

The 6-foot-2, 254-pound Freeny signed as a free agent last month, after serving primarily on the Miami Dolphins’ kicking game for the last few seasons. But with a background playing defensive end at Rutgers, it remains to be seen where the converted outside linebacker will see reps in the Patriots’ defense during OTAs and June minicamp.